In recent years, with the introduction of a myriad of smart handheld devices, user demands for mobile broadband has dramatically increased. For example, the drastic growth of bandwidth-hungry applications such as video streaming and multimedia file sharing are pushing the limits of current cellular systems. One solution to address the increased demand for bandwidth is reliance on device-to-device (D2D) communication functionalities, which allow two nearby devices (e.g., UEs) to communicate with each other in the licensed cellular bandwidth without base station involvement or with limited BS involvement. However, introduction of D2D poses many new challenges and risks to long-standing cellular architecture, which is centered around the base station managing the array of mobile devices within its coverage area.
For example, D2D communication operating concurrently with conventional cellular type wireless communication (e.g., uplink or downlink communication between base station and mobile device(s)) may result in one or both communications experiencing interference on the resources. (e.g., inter-carrier interference (ICI)). Additionally, D2D communication generally requires high transmission power in order to facilitate D2D discovery and the coverage of the D2D direct communication. In such cases, if a D2D device and an existing cellular device use frequency-divided resources in a same subframe, a signal transmitted for a discovery and/or a communication by the D2D device may cause In-Band Emission (IBE) with a channel transmitted to the base station from the existing cellular device. Conversely, if a D2D device and an existing cellular device use time-divided resources in the same frequency band, a signal transmitted for a discovery and/or a communication by the D2D device may cause Inter-Symbol Interference (ISI) with a channel transmitted to the base station from the existing cellular device.
Another issue that arises from D2D communication is the potential for causing misalignment in subframe structure between concurrent conventional cellular communications and D2D communications. For example, in wireless communication networks that operate according to different ones of a plurality of communication technologies (e.g., 5G, 4G/LTE, 3G, Wi-Fi, Bluetooth, etc.), the macro network may operate in accordance with one transmission time interface (TTI) subframe structure while the D2D communication may be limited to a second non-conforming TTI subframe structure. The non-compliance of the frame structures in two communications may result in inefficient spectrum utilization. This is more pronounced when addressing UEs that may have mission critical (MiCr) application (e.g., applications that facilitate remote medical surgeries and require communications that satisfy ultra-reliability and low end-to-end latency). To achieve the reliability and latency requirements of MiCr applications, the macro cell (e.g., base station) associated with a MiCr device may apply a short TTI (e.g., 125 μs) for fast downlink and uplink turn-around between the base station and the MiCr UE. In contrast, D2D communication generally requires long TTI (e.g., 500 μs). The dissimilar characteristics of each with respect to frame structures and varying symbol lengths may result in the communications having different numerology, and thus causing misalignment of communication over the wireless channel.